Numerical investigation of a propeller operating under different inflow conditions

Abstract

This work investigates the flow physics in propeller wakes to better understand how propeller wakes evolve under different inflow conditions from near field to far field. A rotating propeller is numerically modeled by using a dynamic overset technique that involves the improved delayed detached-eddy simulation method. To validate the numerical approach, its results are compared against experimentally determined thrust and torque coefficients and flow fields. The results show that, compared with uniform inflow, turbulent inflow significantly modifies the morphology of the vortex system behind the propeller. Under turbulent-inflow conditions, turbulent structures appear around the boundary layer of the propeller blades and interact with the boundary layer flow of the propeller blades, leading to instability and diffusion of primary tip vortices shed by the blade tips. Multiple local pairing in the circumferential direction leads to the rapid breakdown of the tip vortex system, accompanied by the generation of numerous secondary vortex structures. Tip vortices quickly lose coherence in the middle field and far field and tend to be homogeneously distributed when there is inflow turbulence. The present study gives a deeper insight into the flow physics driving the tip vortex pairing process for a propeller operating under uniform- and turbulent-inflow conditions.